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    SubjectRe: [PATCH V10 09/19] block: introduce bio_bvecs()
    On Thu, Nov 15, 2018 at 04:52:56PM +0800, Ming Lei wrote:
    > There are still cases in which we need to use bio_bvecs() for get the
    > number of multi-page segment, so introduce it.

    The only user in your final tree seems to be the loop driver, and
    even that one only uses the helper for read/write bios.

    I think something like this would be much simpler in the end:

    diff --git a/drivers/block/loop.c b/drivers/block/loop.c
    index d509902a8046..712511815ac6 100644
    --- a/drivers/block/loop.c
    +++ b/drivers/block/loop.c
    @@ -514,16 +514,18 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
    struct request *rq = blk_mq_rq_from_pdu(cmd);
    struct bio *bio = rq->bio;
    struct file *file = lo->lo_backing_file;
    + struct bvec_iter bvec_iter;
    + struct bio_vec tmp;
    unsigned int offset;
    int nr_bvec = 0;
    int ret;

    + __rq_for_each_bio(bio, rq)
    + bio_for_each_bvec(tmp, bio, bvec_iter)
    + nr_bvec++;
    +
    if (rq->bio != rq->biotail) {
    - struct bvec_iter iter;
    - struct bio_vec tmp;

    - __rq_for_each_bio(bio, rq)
    - nr_bvec += bio_bvecs(bio);
    bvec = kmalloc_array(nr_bvec, sizeof(struct bio_vec),
    GFP_NOIO);
    if (!bvec)
    @@ -537,7 +539,7 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
    * API will take care of all details for us.
    */
    __rq_for_each_bio(bio, rq)
    - bio_for_each_bvec(tmp, bio, iter) {
    + bio_for_each_bvec(tmp, bio, bvec_iter) {
    *bvec = tmp;
    bvec++;
    }
    @@ -551,7 +553,6 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
    */
    offset = bio->bi_iter.bi_bvec_done;
    bvec = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
    - nr_bvec = bio_bvecs(bio);
    }
    atomic_set(&cmd->ref, 2);

    diff --git a/include/linux/bio.h b/include/linux/bio.h
    index dcad0b69f57a..379440d1ced0 100644
    --- a/include/linux/bio.h
    +++ b/include/linux/bio.h
    @@ -200,30 +200,6 @@ static inline unsigned bio_segments(struct bio *bio)
    }
    }

    -static inline unsigned bio_bvecs(struct bio *bio)
    -{
    - unsigned bvecs = 0;
    - struct bio_vec bv;
    - struct bvec_iter iter;
    -
    - /*
    - * We special case discard/write same/write zeroes, because they
    - * interpret bi_size differently:
    - */
    - switch (bio_op(bio)) {
    - case REQ_OP_DISCARD:
    - case REQ_OP_SECURE_ERASE:
    - case REQ_OP_WRITE_ZEROES:
    - return 0;
    - case REQ_OP_WRITE_SAME:
    - return 1;
    - default:
    - bio_for_each_bvec(bv, bio, iter)
    - bvecs++;
    - return bvecs;
    - }
    -}
    -
    /*
    * get a reference to a bio, so it won't disappear. the intended use is
    * something like:
    \
     
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      Last update: 2018-11-16 14:46    [W:2.418 / U:0.004 seconds]
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